The present embodiments relates to tissue property ultrasound imaging. Tissue is a viscoelastic material. Changes in tissue on a molecular level may be identified by the viscoelasticity.
One tissue property or component of viscoelasticity is elasticity. Ultrasound imaging may operate in an elasticity imaging mode. U.S. Pat. Nos. 5,107,837, 5,293,870, 5,178,147, and 6,508,768 describe methods to generate elasticity images using the relative tissue displacement between adjacent frames. The tissue strain is determined in response to a stress applied to tissue. The stress is applied externally, such as by manual pressure or by acoustic pressure. Strain, strain rate, modulus (e.g., hardness), or other parameters corresponding to tissue displacement are detected for generating an elasticity image. U.S. Pat. No. 6,558,324 describes methods to represent elasticity using color coding.
Similarly, shear velocity and relaxation time of tissue under stress may be determined. Altered stiffness regions may be identified.